glibc: disable 2.20 for sparc

Disable glibc 2.20 for sparc, it's broken, that leaves 2.21 as the
default in this case.
Fixes bug #7941.

Signed-off-by: Gustavo Zacarias <gustavo@zacarias.com.ar>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

package/glibc/Config.in

@@ -34,6 +34,8 @@ choice
 
 config BR2_GLIBC_VERSION_2_20
 	depends on !BR2_nios2
+	# Broken see https://bugs.busybox.net/show_bug.cgi?id=7941
+	depends on !BR2_sparc
 	bool "2.20"
 
 config BR2_GLIBC_VERSION_2_21